The present invention relates to a deterioration detection method of a composite magnetic head and a magnetic disk inspection apparatus, and specifically to a deterioration detection method of a head in which the number of times of exchanging a composite magnetic head (hereinafter, referred to as a head) due to deterioration is reduced to improve the throughput in an inspection of a magnetic disk in a magnetic disk inspection apparatus using the composite magnetic head including an MR (magnetoresistance effect) head (read head) and a thin-film inductive head (write head).
In recent years, the density of a magnetic disk has been rapidly increased, and an HDD compliant with hundreds of gigabytes to terabytes is mainly used nowadays. With such a high recording density of the magnetic disk, the floating amount of a magnetic head has been decreased.
A slider smaller than 1 mm square is attached to a tip end of a suspension spring with a size of 15 mm to 20 mm in these days, and a distance between a thin-film magnetic head and a disk becomes smaller to few nm to 10 nm.
Performances of such a magnetic head and a head for reading and writing data (magnetic head assembly) are precisely inspected at a manufacturing stage by respective inspection apparatuses.
Especially, for magnetic disk media of a perpendicular magnetic recording-type, a head with a TMR (Tunnel Magnetoresistance) head or a GMR (Giant Magnetoresistance) head is used as an MR head, a distance between the head and the media is set at 10 nm or smaller, and the distance is controlled in some apparatuses.
In an electric inspection of the performance of the magnetic disk, test data is written or read into/from a predetermined track by the head, and the voltage level thereof is evaluated in many cases. Therefore, fluctuations in characteristics due to deterioration of the head cause a problem in the inspection of the magnetic disk.
The composite magnetic disk (hereinafter, referred to as the head) is formed by a thin film forming process, and is fixed to a head slider. The MR head is smaller in shape than an inductive head on the recording side, and a head gap thereof is small. Accordingly, the MR head is vulnerable to various defects such as resistance defects, insulation defects with a shield, and electric characteristic defects, and the head tends to deteriorate in a short term depending on the quality of the MR head.
In addition, in the present situation where a distance between the head and the disk becomes smaller to few nm to ten nm, the head tends to be brought in contact with a recording surface, and stress is applied to the head by the contact or collision. Thus, the head as well as the MR head tends to deteriorate in a short term.
In terms of deterioration of a head, there is known a technique in which fluctuations in characteristics of a head are detected by comparing the gain of AGC for amplifying a read signal from the head at a certain level with a comparison reference value (Japanese Patent Application Laid-Open No. 2004-22119). Further, there is known a technique in which when noise exceeding an acceptable level is generated by detecting a noise signal in a read signal for detecting deterioration of a head, it is determined that the head is deteriorated and the head is magnetized (Japanese Patent Application Laid-Open No. 2006-260652).